Various non-invasive approaches to imaging are known in the art. This can include, for example, the use of x-rays to form one or more images of a given object. Such images can serve a variety of purposes. As but one example in these regards, a number of images of a same object formed using a corresponding variety of x-ray source energies and/or detector spectral responses can facilitate identifying the material (or materials) that comprises that object.
Properly interpreting such images typically presumes a considerable amount of information regarding the imaging spectrum itself. Manufacturers of non-invasive imaging apparatuses often provide general (or even machine-specific) specifications for their machines. For example, information regarding the spectrum utilized by a given apparatus may be characterized as a given number of half-value layers (HVL's). Such information can be useful for many purposes.
Unfortunately, however, such information may be insufficient to accommodate the needs of all application settings. For example, the information may only represent an average or median representation of a family of machines offered by a given manufacturer. As another example such information may be too coarse to support some desired uses.
There have been some attempts in the prior art to estimate the spectral response of a given imaging system. These prior art approaches have utilized, for example, Laplace transform methods, Monte Carlo-based approaches, and even a basis-sum approach. Unfortunately, such approaches are not adequate to address the needs of all application settings.
Elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and/or relative positioning of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention. Certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. The terms and expressions used herein have the ordinary technical meaning as is accorded to such terms and expressions by persons skilled in the technical field as set forth above except where different specific meanings have otherwise been set forth herein.